The present invention relates to improvements in the pouring of molten metals.
It is often desirable during teeming to isolate, as far as possible, molten metal streams from the ambient air to avoid excessive oxidation. In continuous casting, for example, submerged pouring techniques may be adopted. Thus, the molten metal from the teeming ladle may be conducted into the tundish, and/or from the tundish into the mould via an elongated pouring tube which has its lower end submerged beneath the melt surface in the tundish and/or the mould. In common with other tubes or nozzles through which the teeming metal passes, as well as gate valve plates, the elongated pouring tubes are made from refractory materials. Such components are costly in terms of the refractory materials and energy requirements needed to produce them, and attention is turning to production techniques which minimise or avoid the need for high firing temperatures. In the result, there has been a tendency to try materials of rather low refractoriness, including silica, and special concretes. A drawback of such materials is that the molten metal erodes or chemically attacks them quite quickly, and if they are of high thermal conductivity impurities from the molten metal mey build up thereon. Accretion of solids may become quite serious, depending on the metal or alloy to be teemed and the length of the pouring tube. In either event, the useful life of refractory items is undesirably limited.